The LN is in the final arc ... officially the author Stated that the plan is to finish with volume 22 - with the latest volume out in japan is 20 from Sept 22. so its way past this - and the main manga is past this as well as Yukki in the latest chapter mentioned that Hinata is going to meet Rimuru which were the events of chapter 91 -101
That said the LN ending with volume 22 will depend on how much Fuse-san overwrites >P
That said most of the major spinoffs like Trinity, Diaries etc. are spearheaded by Fuse-san ...
in an interview with mipon he said the following
F: "For the manga adaptation, I oversaw pretty much everything, while for spin-off stories, I wrote the plot and answered any questions the staff had. Of course, there are some works for which I handed over full control to the staff. A
As far as I know there is no detail on which have been handed over fully."
That said with the canon ones I expect they still have their plot written by Fuse-san himself ... but that is speculation on my part.
if you read the Light novel Afterwords its full of the author talking about how he ends up going overboard when expanding and adding new material ... much to the Chagrin of the editor.
with the cannon spin-offs being based on his writing that did not make it into the main story, either because of space reasons or because they just did not fit properly. which would fit with him writing the plot for them